While the description of DVCS and HEMP based on the factorization approach is
most general,
in experiments the values of the virtualities \(Q^2\) 
are below the range
required for the validity
of the factorization theorem [1]}, [2]}, [3]}, [4]}, [5]}, [6]}.
Hence, contributions of higher-twist
effects might be substantial (it is an open issue how large these
effects are), which will affect the extraction of
GPDs from the data.
Therefore, it is important to have an effective model for the DVCS and HEMP
amplitudes, which would interpolate between the photoproduction (\(Q^2 \approx 0\) )
and deep inelastic (\(Q^2 \sim {\cal O}({10})\)  GeV\(^2\) ) regimes.
